The present invention relates to a glass material, in particular, a sealing glass, and a magnetic head made by bonding with the sealing glass and a magnetic recording and reproducing apparatus using the magnetic head. Moreover, the glass material of the present invention can have a high strength without increasing a melting point. Therefore, the glass material can be also used for heat resistant parts such as a pannel glass for a cathode-ray tube and a Pyrex glass, and additionally, can be further used for a pannel glass for a liquid crystal display.
Hitherto, a sealing glass which can be handled at a temperature lower than the resisting temperature of various parts has been used for bonding of core materials of magnetic heads to be mounted on magnetic recording and reproducing apparatuses such as VTR or bonding of semiconductor sensors, covering of electronic circuit parts such as IC and LSI, and sealing of electron tubes. When the resisting temperature of the parts is high, sealing glasses of SiO2xe2x80x94B2O3 type or PbOxe2x80x94SiO2 type are used which are relatively high in chemical endurance or mechanical strength, but when the resisting temperature is low, sealing glasses of PbOxe2x80x94B2O3 type are mainly used.
At present, in the case of magnetic heads for VTR, single crystal Mnxe2x80x94Zn ferrites having a saturated magnetic flux density (Bs) of about 5000 gausses are used as the magnetic core materials. Since the resisting temperature of these ferrites is about 800xc2x0 C., glasses of PbOxe2x80x94SiO2xe2x80x94R2O type or ZnOxe2x80x94B2O3xe2x80x94SiO2xe2x80x94R2Oxe2x80x94RO type which can perform the bonding at 700-800xc2x0 C. are used as the bonding glass. Here, R2O means an alkali metal oxide and RO means an alkaline earth metal oxide. With recent development in higher performance magnetic recording and reproducing apparatuses and high-recording density magnetic recording media, Co-based amorphous metal magnetic films or sendust alloy films having a Bs of about 10000 gausses and magnetic films mainly composed of iron element and having a Bs of 12000 gausses or more, such as Fexe2x80x94N or Fexe2x80x94C magnetic films, have been developed for magnetic heads.
These magnetic films have a high saturated magnetic flux density while they are considerably lower in resisting temperature than Mnxe2x80x94Zn ferrites. Therefore, the bonding temperature is lower than 480xc2x0 C. for Co-based amorphous metal magnetic films, about 600xc2x0 C. for sendust alloy films, 500-550xc2x0 C. for Fexe2x80x94N magnetic films, and 550-600xc2x0 C. for Fexe2x80x94C magnetic films. Thus, a PbOxe2x80x94B2O3 sealing glass which can perform the bonding at lower than these resisting temperatures is used as disclosed in JP-A-63-170240, JP-A-63-298807, JP-A-3-265539, JP-A-2-184541, JP-A-2-258649, etc. Moreover, it is proposed to use a V2O5xe2x80x94P2O5 sealing glass as disclosed in JP-A-4-132634.
In the above conventional techniques, no sufficient consideration has been taken to satisfy simultaneously the three conditions of bonding ability at low temperatures of lower than 600xc2x0 C., sufficient mechanical strength and sufficient deaeration. Recently, the demand for high density recording of magnetic recording and reproducing apparatuses is further increased and the magnetic heads mounted thereon are required to have a high output and a sufficient strength to stand the use under further severer conditions. As magnetic core materials which can meet the demands, Fexe2x80x94C or Fexe2x80x94N magnetic films very high in saturated magnetic flux density are studied, and, hence, glasses which can carry out sealing at low temperatures of lower than 600xc2x0 C. must be used.
Furthermore, in order to improve tape touch between the magnetic head and the magnetic recording medium, the sliding width between the magnetic head and the magnetic recording medium must be reduced. Moreover, in order to increase recording capacity, the relative speed of the magnetic head and the magnetic recording medium must be markedly increased than usual.
For these reasons, the glass bonding part of magnetic heads is exposed to the severer use atmosphere. Therefore, the conventional sealing glass capable of performing the bonding at low temperatures are insufficient in mechanical strength and breakage sometimes occurs from the glass bonding part during the sliding of tape. That is, the glasses disclosed in JP-A-63-170240, JP-A-63-298807 and JP-A-3-265539 are insufficient in mechanical strength and can hardly stand the above-mentioned use atmosphere.
The sealing glasses disclosed in JP-A-2-184541 and JP-A-2-258649 are superior in mechanical strength, but since they contain many crystallizing components, viscosity of the glass can be adjusted with difficulty and deaeration can be controlled with difficulty. The sealing glass disclosed in JP-A-4-132634 contains P2O5 and there is the possibility of generation of bubbles produced by water contained in the starting materials.
JP-A-1-138150 discloses a low melting point glass mainly composed of PbO, TeO2, P2O5 and the like, and containing fluorine and rare earth metal oxides, i.e., Y2O3, La2O3 and Gd2O3. However, it is hard to enhance the strength of this type of a glass because the rare earth metal oxides are incorporated into the glass structure and crystalline particles are not generated owing to P2O5 and fluorine contained therein.
An object of the present invention is to provide a sealing glass excellent in low-temperature bonding ability, high in mechanical strength and less in generation of bubbles, a method for producing the glass, and a structure made using the glass.
Another object of the present invention is to provide a magnetic head of high performance and high reliability which can stand severe conditions such as use in high-vision digital VTR and others and a method for making the same, and a magnetic recording and reproducing apparatus of high performance and high reliability on which the magnetic head is mounted.
According to the present invention, there is provided a glass containing a rare earth element and crystalline particles. The glass can be used for a sealing glass and heat resistant parts such as a pannel glass for a cathode ray tube and the like.
The sealing glass of the present invention for attaining the above objects is a sealing glass containing at least one rare earth element and, in this glass, fine particles are uniformly dispersed in its matrix. Said fine particles contain at least one of rare earth elements. These rare earth elements are Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu. Furthermore, the fine particles have a particle size of 1-50 nm, more preferably 3-10 nm. Moreover, the fine particles are crystalline. Said matrix contains a heavy metal oxide and boron oxide and/or silicon oxide. The heavy metal oxide is preferably an oxide of lead.
The sealing glass of the present invention contains, in terms of the following oxides, PbO: 44-91% by weight, B2O3: at least 6% by weight, SiO2: 0-30% by weight, the total content of B2O3 and SiO2: 6-40% by weight and Ln2O3 (Ln: Pr, Nd, Sm. Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu): 0.3-2.9% by weight, and fine particles are uniformly dispersed therein. More preferably, the sealing glass contains, in terms of the following oxides, PbO: 44-77% by weight, B2O3: 6-20% by weight, SiO2: 0-30% by weight, the total content of B2O3 and SiO2: 6-40% by weight, at least one of ZnO, Al2O3 and R2O (R: an alkali metal element): 0-25% by weight and Ln2O3 (Ln: Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu): 0.5-1.5% by weight, and the fine particles are uniformly dispersed therein.
Furthermore, the sealing glass of the present invention is a sealing glass containing at least one of rare earth elements, and in this glass, fine particles and low-expansion fillers are uniformly dispersed in the matrix. Said fine particles contain at least one of the rare earth elements. The rare earth elements are Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu. The fine particles have a particle size of 1-50 nm and the matrix contains an oxide of lead and boron oxide and/or silicon oxide. The low-expansion filler is at least one of zirconium silicate, lead titanate, xcex2-eucryptite, and silica glass.
The method for producing the glass according to the present invention includes a step of heating a mixed powder of glass raw materials in a crucible to obtain a glass melt, a step of precipitating fine particles in the glass melt, a step of continuously stirring the glass melt by vibration generated by a vibrator provided in contact with outer wall of the crucible, a step of cooling the glass melt to obtain a glass, and a step of reheating the glass and annealing it. The raw materials for the glass contain the elements of rare earth, lead, and boron and/or silicon. The rare earth elements are Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu. The fine particles have a particle size of 1-50 nm.
Furthermore, the structure of the present invention comprises at least a substrate and a sealing glass coated on the surface thereof, and this sealing glass contains at least one of rare earth elements and comprises a matrix in which fine particles are uniformly dispersed. The structure further comprises at least a pair of substrates and a sealing glass provided therebetween. The pair of the substrates are bonded with the sealing glass, and this sealing glass contains at least one of rare earth elements and comprises a matrix in which fine particles are uniformly dispersed.
Said fine particles contain at least one of rare earth elements. The rare earth elements are Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu. The fine particles have a particle size of 1-50 nm and the matrix contains an oxide of lead and boron oxide and/or silicon oxide.
Next, the magnetic head of the present invention comprises a pair of magnetic cores, a non-magnetic gap material provided between the magnetic cores and a sealing glass which bonds the pair of the magnetic cores. This sealing glass contains at least one of rare earth elements and comprises a matrix in which fine particles are uniformly dispersed. The fine particles contain at least one of the rare earth elements. The rare earth elements are Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu. The fine particles have a particle size of 1-50 nm, preferably 3-10 nm, and the matrix contains an oxide of lead and boron oxide and/or silicon oxide.
The magnetic head of the present invention comprises a pair of magnetic cores, a non-magnetic gap material provided between the magnetic cores and a sealing glass which bonds the pair of the magnetic cores. The sealing glass contains, in terms of the following oxides, PbO: 44-77% by weight, B2O3: 6-20% by weight, SiO2: 0-25% by weight, the total content of B2O3 and SiO2: 6-30% by weight, Ln2O3 (Ln: Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu): 0.5-1.5% by weight and the remainder of at least one of Al2O3, ZnO and R2O (R: an alkali metal element), and fine particles are uniformly dispersed therein. The above sealing glass has a micro Vickers hardness Hv of 425 or higher. Said magnetic core comprises a support on which a magnetic film is formed, and more preferably, the magnetic film is a Fe-based film.
The magnetic head of the present invention comprises a pair of magnetic cores on which magnetic films are formed, only the gap part being butting faces, a non-magnetic gap material provided between the pair of the magnetic cores and a sealing glass, and this sealing glass bonds the butting faces to each other. The sealing glass contains at least one of rare earth elements and this glass comprises a matrix in which fine particles are uniformly dispersed. Said fine particles contain at least one of rare earth elements. The rare earth elements are Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu. The fine particles have a particle size of 1-50 nm, more preferably 3-10 nm. Said matrix contains an oxide of lead and boron oxide and/or silicon oxide. More preferably, the magnetic film is Fe-based film. It is preferred that the sliding width between the magnetic head and the recording medium is 65 xcexcm or less.
The method for making the magnetic head according to the present invention includes a step of forming a non-magnetic gap material at the butting part of at least a pair of magnetic cores, a step of butting the pair of the magnetic cores, a step of sealing them with a sealing glass containing at least one of the rare earth elements, and a step of precipitating fine particles in the sealing glass. The step of precipitating the fine particles is conducted by a heat treatment at a temperature lower than the resisting temperature of the magnetic cores. The fine particles contain at least one of rare earth elements. The rare earth elements are Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu. The fine particles have a particle size of 1-50 nm, more preferably 3-10 nm. The sealing glass contains an oxide of lead and boron oxide and/or silicon oxide.
The magnetic recording and reproducing apparatus of the present invention is provided with at least magnetic heads comprising a pair of magnetic cores composed of a support on which a magnetic film is formed, said magnetic cores being bonded with a sealing glass through a non-magnetic gap material, a cylinder part fitted with a plurality of the magnetic heads, a driving part for the cylinder part, and a control part carrying out the information processing from the information recording medium. The sealing glass contains at least one of rare earth elements and comprises a matrix in which fine particles are uniformly dispersed.
The fine particles contain at least one of the rare earth elements. The rare earth elements are Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu. Furthermore, the fine particles have a particle size of 1-50 nm, more preferably 3-10 nm. Said matrix contains an oxide of lead and boron oxide and/or silicon oxide.
Furthermore, the magnetic recording and reproducing apparatus of the present invention is provided with a magnetic head constructed of a pair of magnetic cores having magnetic films, only the gap parts thereof being butting faces, a non-magnetic gap material provided between the pair of the magnetic cores and a sealing glass which bonds the butting faces to each other; a jig for fitting one or more of the magnetic heads; a cylinder part fitted with a plurality of the fitting jigs; a driving part for the cylinder part; and a control part which carries out processing of information from the information recording medium. The sealing glass contains at least one of rare earth elements and comprises a matrix in which fine particles are uniformly dispersed. The fine particles contain at least one of said rare earth elements, and the rare earth elements are Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu. Furthermore, the fine particles have a particle size of 1-50 nm, more preferably 3-10 nm. Said matrix contains an oxide of lead and boron oxide and/or silicon oxide. In the magnetic head mounted on the magnetic recording and reproducing apparatus of the present invention, the magnetic film is preferably Fe-based film, and desirably, the sliding width between the magnetic head and the recording medium is 65 xcexcm or less. Moreover, the relative speed of the magnetic head and the recording medium is preferably 20 m/sec or more.
The present invention resides in a sealing glass, characterized in that the glass comprises, in terms of the following oxides and by weight, 30-93% of PbO, 25% or less of B2O3 and 30% or less of SiO2 and has a micro Vickers hardness of 370 or higher and the viscosity of the glass reaches 104 poises at 600xc2x0 C. or lower.
Furthermore, the present invention resides in the above sealing glass, characterized in that the glass additionally contains at least one of 10% or less of Al2O3, 15% or less of ZnO, 15% or less of Na2O, 15% or less of K2O, 15% or less of Bi2O3, 10% or less of TeO2, 10% or less of Fe2O3, 5% or less of SrO and 5% or less of TiO2 and, optionally, Ln2O3 (Ln is at least one of Sc, Y, La and lanthanides).
The present invention resides in a high-definition magnetic recording and reproducing apparatus, characterized in that the apparatus is provided with magnetic heads comprising a pair of magnetic cores composed of a magnetic film formed on a support, said magnetic cores being bonded to each other with a sealing glass through a non-magnetic gap material; a cylinder part fitted with a plurality of the magnetic heads; a driving part for the cylinder part; and a control part which carries out processing of the information from the information recording medium comprising a tape having a metal magnetic film, and that the relative speed of the cylinder part and the information recording medium is 20 m/sec or higher or 50 m/sec or higher, the sliding width between the magnetic head and the information recording medium is 65 xcexcm or less, and the time required for breaking the magnetic head by rotation of the cylinder part and sliding with the information recording medium is 500 hours or more.